Fair question to which you'll end up with a vague answer as I don't have the command history to look back since restoring the backup.
The tabs I had open for trying to do the upgrade instructed me to:
Code:
# Install update-manager-core
sudo apt-get install update-manager-core
# update your installation of Ubuntu
sudo apt-get update
sudo apt-get upgrade
# Launch the upgrade tool
sudo do-release-upgrade
That failed do to the sources issue, so I found
this page on ubuntu.com which instructed me to do this after fixing the sources:
Code:
sudo aptitude update && sudo aptitude safe-upgrade
sudo do-release-upgrade
It's possible, now that I recount that, that ll I had to do was fix the sources and then go through the first set of instructions but that did not occur to me at the time.